The Noble gases or group 0 are colourless gases at room temperature. They are mono-atomic meaning their gases exist as single atoms, not molecules. They are chemically inert, meaning they don't react with anything because they have a full outer shell and don't give up their electron very easily. Because the noble gases are inert, they're also non flammable which has, combined with the other properties, made them very hard to observe and meant they weren't discoverer till very late.
Noble gases can be used to provide an inert atmosphere like argon does in filament bulbs, to stop the filament from burning away.Argon and Helium can be used to protect metals that are being welded as the inert atmosphere stops the metal from reacting with oxygen in the air. Helium is used in airships and party balloons, helium has a lower density than air so i will make them float and it is no flammable which makes it less dangerous than Hydrogen gas.
Melting point, boiling point and density decrease as you go down group 0.